Fluoroelastomer are synthetic rubbers designed for demanding service applications in hostile environments, endowed with outstanding chemical and thermal resistance.
Perfluoroelastomers having fully fluorinated backbones and typically based on copolymers of tetrafluoroethylene (TFE) and perfluoromethylvinylether (MVE), optionally comprising recurring units derived from cure-site containing monomers, represent in this domain top-edge class of materials, introduced into the market since late sixties.
Generally these TFE/MVE copolymers have roughly a 60/40 to 65/35 mol/mol composition, which enables achievement of required elastomeric behaviour; such copolymers generally also comprise recurring units derived from monomers comprising curing sites and/or end groups contemplating such cure sites. Typically, peroxide curing is preferred technique used for their vulcanization and moulding.
In the domain of fluoroplastomers, copolymers of TFE and perfluoroalkylvinylethers, in particular MVE, are also well-assessed materials. In this domain, combination of two or more perfluoroalkylvinylethers, has been already suggested.
Thus, EP 633274 A (AUSIMONT SPA) 11 Jan. 1995 discloses thermoprocessable copolymers of tetrafluoroethylene comprising recurring units derived from perfluoromethylvinylether and from at least one additional fluoromonomer, like, notably perfluoroethylvinylether. Similarly, WO 2007/096348 (SOLVAY SOLEXIS SPA) 30 Aug. 2007 discloses thermoplastic terpolymers of tetrafluoroethylene, perfluoromethylvinylether and perfluoroethylvinylether, suitable for extrusion moulding cable sheathings.
Amorphous plastomers of tetrafluorethylene, perfluoromethylvinylether and perfluoroethylvinylether have been aso described in the past. Thus, U.S. Pat. No. 5,919,878 (E.I. DUPONT DE NEMOURS) 6 Jul. 1999 discloses amorphous terpolymers of TFE, MVE and perfluoroethylvinylether (EVE) suitable as thermoplastic coating. Similar amorphous copolymers, suitable as adhesive or coating compositions are also known from WO 99/32234 (DU PONT) 1 Jul. 1999, EP 1093485 A (DU PONT) 25 Apr. 2001, U.S. Pat. No. 6,880,238 (DU PONT) 19 Apr. 2005, U.S. Pat. No. 7,049,365 (E. I. DU PONT DE NEMOURS AND COMPANY) 15 Jul. 2004. Nevertheless, all these documents do not pertain to the domain of peroxide curable fluoroelastomers, nor teach about sealing properties of cured materials therefrom.
While thus terpolymers of TFE, MVE and perfluoroethylvinylether (EVE) are well-known in the art as thermoplastic materials, little or nothing is known about effects of modifying a curable perfluoroelastomer by addition of EVE for obtaining cured articles, in particular for improving thermal resistance.